Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B29/00—Combined heating and refrigeration systems, e.g. operating alternately or simultaneously
  • F25B29/006—Combined heating and refrigeration systems, e.g. operating alternately or simultaneously of the sorption type system
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
  • C09K5/02—Materials undergoing a change of physical state when used
  • C09K5/04—Materials undergoing a change of physical state when used the change of state being from liquid to vapour or vice versa
  • C09K5/047—Materials undergoing a change of physical state when used the change of state being from liquid to vapour or vice versa for absorption-type refrigeration systems

Definitions

• This invention relates to a process of using a working fluid in a heat pump.
• Water is a desirable working fluid for adsorption heat pumps because of its high latent heat of. vaporisation and because it is nontoxic. However it has two -disadvantages, namely its relatively high freezing point and its low vapour pressure at desirable evaporation temperatures.
• organic freezing point depressant may be used which does not appreciably lower the partial pressure of water vapour above the solution and which will allow water to be used in conjunction with hydrophobic adsorbents such as activated charcoal.
• This organic depressant is n-propanol and it forms an azeotrope with water, the weight per cent of water varying from about 28 to 32 according to the temperature.
• a process of sorption is one in which an azeotrope of n-propanol and water is sorbed by sorbent, thereby evolving heat of sorption.
• sorbate we mean respectively "absorbate or adsorbate”, “absorbent or adsorbent” and “absorption or adsorption”.
• the azeotrope of n-propanol and water has been found to have the following properties:
• This azeotrope can be used in adsorption or absorption processes.
• the adsorbent will usually be a substance like a zeolite molecular sieve, e.g. the 4Aor Y type, activated charcoal and silica gel.
• the adsorbate i.e. n-propanol-water azeotrope
• heat of adsorption will be evolved and this heat can be transferr elsewhere, for example to another partof a heat pump or for delivery to the load.
• This transfer is usually carried out by heat exchange, by the use for example of a heat exchanger, the coils of which are housed inside the adsorber and which are surrounded by adsorbent.
• the azeotrope After adsorption the azeotrope will have to be desorbed from the adsorbent if the process is to be cyclic. This is usually achieved by insertion of a heat exchanger in the adsorbent housed in the adsorber. Alternatively an electrical resistive heater can be located in the adsorbent housed in the adsorber.
• Systems employing an adsorber also make use of a heat of fusion heat store.
• the adsorbate vapour which is driven off from the adsorber is usually condensed in the heat of fusion heat store.
• heat stores there is a plurality of receptacles housing a substance with a relatively high melting point and a relatively high heat of fusion, for example stearic acid.
• the heat of condensation of the adsorbate as it condenses in the heat of fusion heat store is transmitted to this relatively low melting substance which then melts. In this way heat is stored in this .substance housed in the receptacles. When heat is abstracted from this heat store the substance freezes, evolving latent heat of fusion.
• Processes and systems involving the adsorption of an adsorbate by an adsorbent and where an n-propanol-azeotrope can be used as the adsorbate include those claimed in our prior patent applications GB8038283, (European 81305627:2), GB 8039157 and GB 8111392.
• the absorption process can be the conventional process of absorption wherein absorbate is driven off from a generator by heat supplied externally, vaporised absorbate is condensed in a condenser, rejecting heat of condensation, condensed absorbate after being expanded is sent to an evaporator where it evaporates and from the evaporator vaporised absorbate is delivered to an absorber where the heat of absorption is rejected.
• Weak working fluid i.e. absorbate plus absorbent
• strong working fluid is delivered from the generator to the absorber via an expansion valve.
• Such an absorption process can be used in conjunction with an adsorption process as described in our -GB patent application 8039157 wheren the heat supplied to the generator is obtained from the latent heat of condensation of adsorbate vapour, said vapour being desorbed from adsorbent housed in an adsorber.
• Another such process is that described in ourGB patent application 8017030 wherein the heat supplied to the generator is obtained from a solar panel or other source of heat.
• a sorber was charged with a gel of lithium bromide and n-propanol-water azeotrope supported in a porous matrix of coke breeze.
• the azeotrope was evaporated from an evaporator at a temperature of below 0°C and sorbed by the sorbent.. Heat of sorption was evolved at a temperature of above 60°C and delivered to the load.
• this azeotrope was desorbed by heat from a resistive heat and then passed to a condenser and the azeotrope was then condensed in a heat of fusion heat store and returned to the evaporator. This cycle of .sorption and desorption was then repeated indefinitely.
• GB Apolication 8038283 claims a heating system wherein solar energy is used to supply heat to a heat of fusion heat store, adsorbate is stripped from adsorbent in an adsorber and thereafter condensed, the heat of condensation being delivered to the load, condensed adsorbate is sent to an evaporator J adsorbate is vaporised in the evaporator and vaporised adsorbate is adsorbed in the adsorber, the heat of adsorption being delivered to the load.
• GB Application 8039157 claims a combined adsorption and absorption process in which an external source of heat is used to desorb adsorbate from adsorbent housed in an adsorber.
• the adsorbate vapour is condensed and the latent heat of condensation used to remove absorbate from the working fluid in the generator of an absorption system.
• GB Application 8111392 claims a method of obtaining heat wherein adsorbate is evaporated from an evaporator and thereafter adsorbed by an adsorbent in.an adsorber, the latent heat of adsorption providing heat to the load and thereafter the adsorbate is desorbed from the adsorbent and desorbed adsorbate condensed.in a.heat of fusion heat store and the substance housed therein melting and thereafter solidifying, the latent heat of fusion providing heat to the load.
• the absorbent is for example an aqueous alkali metal halide, e.g.aqueous lithium bromide or lithium chloride.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Combustion & Propulsion (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Sorption Type Refrigeration Machines (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=10521898

Family Applications (1)

Country Status (3)

Citations (7)

• 1981
  • 1981-05-19 GB GB8115312A patent/GB2098623B/en not_active Expired
• 1982
  • 1982-05-14 DE DE8282302464T patent/DE3260941D1/de not_active Expired
  • 1982-05-14 EP EP19820302464 patent/EP0065858B1/fr not_active Expired

Patent Citations (7)

Also Published As

Similar Documents

Legal Events